I wrote a small script that basically displays 20 to 30 categories on a page which a user has the option toeither select one or multiple items from the list. For the sack of argument the user selected the following items from the list:

would going with option number 2 would create a lot of repetitive entries. yes for different users but the table still would hlod repetitive info.

don't worry about it

imagine a table containing people's addresses -- there's a column for country, right? and many people would have 'CA' or 'US' as their country, right? is this repetitive? i suppose, but there's no way you'd want to try to avoid this

same with your user categories... sure, multiple users might select the same category, but there's no way you'd want to try to avoid this